Mechanical tuning adjuster



Oct. 17, c pl o "ECHANICAL TUNING ADJUSTER Filed March 27, 1945 CHARLESPno/v Patented l7,

MECHANICAL TUNING ADJUSTER Charles Piton, Geneva, Switzerland, assignor,by mesne assignments, to Hermann Thorens S. A., a corporation ofSwitzerland Application March 27, 1945, Serial No. 585,088 InSwitzerland May 5, 1944 8 Claims.

In radio receivers, transmitters, and amplifiers in general of theelectronic-tube type, there are employed circuits, the characteristicsof which must be adjustable at will (coupling, damping, frequency etc.).For this purpose, the designers have devised oscillation-circuitsequipped with at least one adjustable circuit-element. This element mayfor example be constituted by the movable armature of a condenser, bythe plunger-core or another part of the magnetic circuit of an inductioncoil, by a coil displaceable with respect to another coil (variometer)etc. or by any adjustable element of an electric oscillation-circuit,the position of which defines at least one of the characteristics of thecircuit of which it forms a part.

Generally speaking. it is advantageous, that the variation of thecharacteristics of an electric circuit be a linear function of thedisplacement of the device controlling the displacement of theadjustable element. In most cases, the variation of the characteristicsof the oscillationcircuit is not proportional to the value of thecharacteristics defining it (the frequency of an oscillation-circuit isneither proportional to the capacity nor to the self-inductance of thiscircuit, but is a function of both; the damping is also a non-linearfunction of the resistance of the oscillation-circuit and the couplingbetween two oscillation-circuits does not vary in a linear manner as afunction of the distance separating the two elements of the circuits).

If it is desired that the variation of the characteristics of anelectric oscillation-circuit be a linear function of the displacementsof the controlling-device, the designers have tried to shape either theadjustable part or the stationary part of the circuit-element in such amanner, as to obtain the result that the variations of the elementdetermining the variations of the circuitcharacteristics are not alinear function of the displacements of the controlling device. Thesedevices make it often necessary to employ complicated shapes for certainelements of the said oscillation-circuit and to increase their dimen- 5sions.

The object of the present invention is to provide a control-device forcontrolling the displacements of an adjustable element of an electricoscillation-circuit, control-device which controlleast onetransmission-member having a transmission-ratio variable according to acontinuous function of the position of the control-device.

Another object of the invention is to provide a control-device by whichthe adjustable element of the oscillation-circuit is displaced in atranslatory manner with respect to the stationary part of the circuitand is connected mechanically to a control-device by the intermediarymeans of at least one transmission-member having a transmission-ratiovarying according to a continuous function of the position of thecontroldevice.

The said adjustable element may be fixed on a shaft arranged to slide inan axial direction, or arranged to rotate with respect to the stationarypart of the circuit. Further this shaft may be displaced in a combinedtranslatory and rota-' for controlling the displacements of the movablearmature of a variable condenser.

Figure 2 shows a cross-section along the line A-B of Fig. 1.

Figure 3 shows a longitudinal cross-section of a second form ofexecution of the control-device.

Figure 4 is a cross-section along the line CD of Figure 3, and

Figure 5 is a cross-section along the line E-F of the same figure.

Figures 6, 7 and 8 show axial cross-sections of three other forms of thecontrol-device.

In the forms of invention represented by the Figs. 1 and 2 the device isapplied to a variable condenser comprising mobile and stationaryarmatures, these armatures being formed of a number of metallic,co-axial and concentric cylinders limited at their ends by planesperpendicular to their generating lines. The mobile armatures aredisplaceable axially in such a manner as to have the cylinder-electrodesof the mobile armature penetrate between the cylinder-electrodes of thestationary armature. In this type of condenser, the variations of thecapacity is a linear function of the axial displacement of the mobilearmature and the variation of the frequency of the circuit of which itforms part is a non-linear function of this displacement.

In the example shown in Figures 1 and 3, the stationary armatures of thecondenser comprise circular plates ll carrying the stationary cylinders12, the plates ll being fastened to the housing 13 by means of severalinsulators [4. In the end-walls [5 of the housing are provided twobearings !6, in which a shaft l7 carrying the mobile armatures can movefreely. Each of the mobile armatures is provided with a circular platel8 carrying a series of cylinders i9 which penetrate between thestationary cylinders 12. In one of the bearing-bodies is fastened ashaft on which turns freely a pulley 2! provided with groove 22 intendedfor receiving a cable 23 actuated by a control-device 24. This pulley isprovided with a helicoidal ramp 25 of variable pitch in contact with oneend of the shaft H and controlling the longitudinal displacements of thesame. A spring 26 located between one of the bearings and the mobilearmature tends to maintain the shaft in contact with this ramp, thepitch of which is so chosen as to alter the capacity according to agiven function of the angular displacements of the pulley 2i, whichdisplacements are controlled by the displacements of the control device.

In the form of invention described, the capacity of the condenser is alinear function of the i;

axial displacements of the mobile armature with respect to thestationary armature, but this mobile armature is connected to thecontrol-device by the intermediary of a transmission-device providedwith the helicoidal ramp of variable pitch 25. For this reason thetransmission-ratio of the displacements between the control-device andthe mobile armature is a function of the relative positions of themobile and stationary armature. The pitch of the ramp may vary accordingto any continuous function and may be chosen in such a manner, that thevariation of the capacity as a function of the displacements of thecontrol-device follows a predetermined continuous curve. Thecontrol-device may comprise a knob 2? equipped with an index-pointer 28indicating directly on a dial 29 the frequencies of the circuit of whichthe condenser constitutes a part. In an alternative form of invention,the cable connecting the pulley 2! to th controldevice may carry anindex-pointer which is displaced transversely over a graduated dial. Thecontrol-device may furthermore be constituted by a hand operated knobfixed to the pulley 2i.

In the form of invention represented by the Figures 3, 4 and 5 thecondenser is constituted by half-cylindric plates 38 and 3!, limited bya plane passing through two generating lines. The mobile armaturecomprises a half-circular plate 32 fastened to the shaft i! which turnsin the bearings [6. In this case the variation of the capacity is afunction of the angular displacements of the mobile armature withrespect to the stationary armature. The intermediate transmission deviceeffecting a variable transmission-ratio according to the relativepositions of the mobile and stationary armatures, is constituted by apulle 33 with a spiral groove, fastened to the shaft l 7 and driven by acable, which is fixed at one of its ends to the periphery of the pulleyand at its other end to a control-device not shown on the drawing. Theradius of the groove of the pulley is variable and increases in acontinuous manner. The variation of the transmission-ratio of thedisplacements between the control-device and the armature is a functionof the law governing the increase of the radius of the pulley and maytherefore correspond to a predetermined continuous function. A spring34, one end of which is fixed to the pulley 33 and 4 the other end tothe wall [5 assures the tension of the cable.

In the form of invention represented in the Figures 6, '7, and 8, theshaft I1 operating the variable element of the oscillation-circuitexecutes a combined translationary and angular displacement. In the formof invention shown in Fig. 6, the shaft l1 carries a thread of constantpitch in which engages a finger 35 fastened to one of thebearing-bodies. The angular displacements of the mobile armature or anyadjustable element of the oscillation-circuit are therefore directlyproportional to these axial displacements. The intermediatetransmission-device enabling the variation of the transmission-ratio ofthe displacements between the control-device and the mobile armature isformed by a pulley 36 provided with a helicoidal groove 31 ofprogressively increasing radius, this groove receiving a cable connectedto a control-device. This pulley not only constitutes atransmission-device of variable ratio, but also a speed reducer, sincethe total axial course of the mobile armature necessitates severalrevolutions of the pulley 36.

In the form of invention shown in Fig. 7, the intermediarytransmission-device is constituted by a helicoidal groove 38 of variablepitch provided in the shaft H, with which groove engages a finger 39fixed to the bearing-body H5. The shaft is driven by a pulley with acircular groove 48. In an alternative form of this form of invention,the helicoidal groove could be provided in the body of the bearing 16and the finger could be fixed to the shaft 17.

In the form of invention represented in Figure 8, the shaft I? slidesfreely in the bearings 56. On this shaft is fixed a cam 4! provided witha helicoidal ramp, the pitch and the radius of which are progressive. Acircular disc 43 turning and Sliding freely on a fixed shaft 44 ismaintained in contact with this ramp 42 by means of a spring 45 and bymeans of another spring 49 placed on the shaft I l and abutting aportion of the housing l3 (not shown). The spring 1 45 may be omitted ifthe ramp is provided with an exterior collar guiding the disc 63. Theshaft I! is driven by a pulley 46 with circular groove, connected by acable to a control-device (not shown). The intermediary transmissiondevice of variable ratio, constituted by the cam 45 is also aspeed-reducer. The angular and axial displacements of the mobilearmatures are limited by stops 4'! fixed to the housing and againstwhich come to bear the pins 48 provided on the periphery of the cam. Inan alternative form, the cam may be fastened to the housing and the discmay turn and slide on a shaft fixed to the shaft I1.

I claim:

1. In an electric oscillating circuit comprising a mechanicallyadjustable tuning element. control means for controlling the position ofsaid tuning element, and a mechanical transmission device fortransmitting movement from said control means to said tuning element,said transmission of movement taking place with a variable transmissionratio varying continuously from one position to another of said controlmeans. said mechanical transmission device comprising a shaft, means forrotating said shaft, a revolving cam provided with a contact ramp andmounted on said shaft, a mechanical contact member contacting said camon said ramp, and resilient means urging the ramp of said cam axiallyagainst said contact member, said shaft driving said tuning element,wherein said ramp of said cam has the shape of a spirally wound helicoidwith two independent parameters, said helicoid extending oversubstantially more than one complete turn around said shaft, one of saidtwo parameters varying as a continuous function of the angle measuredaround the axis of said shaft, whereby there is produced a transmissionof movement with continuously varying transmission ratio and where .avery large angle of rotation of said cam is made to correspond to a versmall displacement of said tuning element in said oscillating circuit.

2. In an electric oscillating circuit, a transmission device accordingto claim 1, wherein the second parameter of said spirally Wound helicoidvaries as a continuous function of the angle measured around the aXis ofsaid shaft.

3. In an electric oscillating circuit, a mechanical transmission deviceaccording to claim 1 wherein said tuning element is mounted rigidly onsaid shaft.

4. In an electric oscillating circuit, a mechanical transmission deviceaccording to claim 1, wherein the generating line of said helicoid has aportion directed substantially in a radial direction relative to theaxis of the helicoid, the spirally wound helicoid thus provided beingadapted to cooperate with the contact member to transmit a substantialaxial thrust ulpon rotation, said thrust causing an axial displacementof said cam and shaft.

5. In an electric oscillating circuit a mechanical transmission deviceaccording to claim 1, wherein the generating line of said helicoid has aportion directed substantially in a radial direction relative to theaxis of the helicoid, the spirally wound helicoid thus provided beingadapted to cooperate with the contact member to transmit a substantialaxial thrust upon rotation, said mechanical contact member being mountedslid ably on a stationary guiding surface directed sub stantially atright angles with said shaft, said resilient means acting axially onsaid shaft, said thrust causing an axial displacement of said cam andshaft.

6. In an electric oscillating circuit a mechanical transmission deviceaccording to claim 1, wherein the generating line of said helicoid has aportion directed substantially in a radial direction relative to theaxis of the helicoid, the spirally wound helicoid thus provided beingadapted to cooperate with the contact member to transmit a substantialaxial thrust, said mechanical contact member being a roller mountedrevolubly and slidably' on a stationary stub shaft directedsubstantially at right angles with said shaft, said roller being backedby a spring urging same towards said shaft, said ramp of said cam beingkept in contact with the rim of said roller by the resilient meansacting axially on said shaft, said thrust causing an axial displacementof said cam and shaft.

7. In an electric oscillating circuit comprising a mechanicallyadjustable tuning element, control means for controlling the position ofsaid tuning element, and a mechanical transmission device fortransmitting movement from said control means to said tuning element,said transmission of movement taking place with a variable transmissionratio varying continuously from one position to another of said controlmeans, said mechanical transmission device comprising a shaft, means forrotating said shaft, a cam provided with a contact ramp and mountedcoaxially with respect to said shaft, a mechanical contact membercontacting said ramp on said cam and resilient means urging said ramp ofsaid cam and said contact member against one another, said ramp of saidcam having the shape of a spirally wound helicoid with two independentparameters, said helicoid extending over substantially more than onecomplete turn around said shaft, one of said two parameters varying as acontinuous function of the angle measured around the axis of said shaft,whereby there is produced a transmission of movement with continuouslyvarying transmission ratio and where a very large angle of rotation ofsaid control means is made to correspond to a very small displacement ofsaid tuning element in said oscillating circuit.

8. In an electric oscillating circuit comprising a mechanicallyadjustable tuning element, control means for controlling the position ofsaid tuning element, and a mechanical transmission device fortransmitting movement from said control means to said tuning element,said mechanical transmission device comprising a rotary element actuatedby said control means, a cam member mounted coaxially with respect tosaid rotary element and having a contact ramp in the form of a conicalspiral extending through an arc of more than 360, a mechanical contactmember contacting said ramp on the cam member, resilient means urgingsaid cam ramp and said contact member into contact with each other,means driven by the rotary element for effecting relative rotationbetween the contact and cam members about the axis of the rotatingelement, and means for transmitting motion, resulting from the cammingaction between said ramp and contact members on relative rotation, tosaid tuning element.

CHARLES PITON.

REFERENCES CITED The following references are of record in the file ofthis patent:

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